Identification of the Mammalian DNA‐Binding Protein P8 as Glyceraldehyde‐3‐Phosphate Dehydrogenase

Abstract

The DNA‐binding protein P8 from transformed hamster fibroblasts (line NIL‐1‐hamster sarcoma virus) has been purified to homogeneity by DNA‐cellulose and phosphocellulose chromatography. The molecular weight of dissociated P8 is 36000, the same as that reported for the subunits of glyceraldehyde‐3‐phosphate dehydrogenase, and the mobility of these proteins in polyacrylamide gels is identical. The amino acid composition of P8 is very similar to that of glyceraldehyde‐3‐phosphate dehydrogenase. When assayed for glyceraldehyde‐3‐phosphate dehydrogenase activity the P8 preparation had a specific activity of 54.6 units/mg, a value comparable to that of the crystalline enzyme from several sources. Furthermore, serum prepared against P8 crossreacts with glyceral‐dehyde‐3‐phosphate dehydrogenase from hamster muscle. These results show that P8 is glyceraldehyde‐3‐phosphate dehydrogenase. The interaction of P8 from transformed fibroblasts and glyceral‐dehyde‐3‐phosphate dehydrogenase from hamster and rabbit muscle with DNA has been studied using a Millipore filtration technique. These proteins have affinity for single‐stranded DNA but not for double‐stranded DNA. Copyright © 1977, Wiley Blackwell. All rights reserved